Atomic motions in the $\alpha \beta$-region of glass-forming polymers: Molecular versus Mode Coupling Theory approach

Abstract

We present fully atomistic Molecular Dynamics simulation results on a main-chain polymer, 1,4-Polybutadiene, in the merging region of the $\alpha$- and $beta$-relaxations. A real space analysis reveals the occurrence of localized motions (``$\beta$-like'') in addition to the diffusive structural relaxation. A molecular approach provides a direct connection between the local conformational changes reflected in the atomic motions and the secondary relaxations in this polymer. Such local processes occur just in the time window where the $\beta$-process of the Mode Coupling Theory is expected. We show that the application of this theory is still possible, and yields an unusually large value of the exponent parameter. This result might originate from the competition between two mechanisms for dynamic arrest: intermolecular packing and intramolecular barriers for local conformational changes (``$\beta$-like'').

10 pages, 6 figures

References in corpus (5)

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• Anomalous Dynamic Arrest in a Mixture of Big and Small Particles
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Cited by in corpus (6)

• Molecular dynamics simulations of glassy polymers
• Dynamic Arrest in Polymer Melts: Competition between Packing and Intramolecular Barriers
• Conformational and Structural Relaxations of Poly(ethylene oxide) and Poly(propylene oxide) Melts: Molecular Dynamics Study of Spatial Heterogeneity, Cooperativity, and Correlated Forward-Backward Motion
• The Role of Intramolecular Barriers on the Glass Transition of Polymers: Computer Simulations vs. Mode Coupling Theory
• Tests of mode coupling theory in a simple model for two-component miscible polymer blends
• Glassy dynamics of a binary Voronoi fluid: A mode-coupling analysis